This is a prospective, multicenter, observational study of HIV-infected subjects who are CMV-seropositive and who have not had clinical symptoms of CMV disease at study entry. Subjects will be followed for three years or until the diagnosis of CMV end-organ disease, or death, whichever comes first. Clinical evaluations will be performed at baseline and every 8 weeks. Blood samples for virologic studies will be obtained every 16 weeks. Blood samples will also be stored every 16 weeks for future immunologic studies. Routine clinical evaluations will be performed prior to enrollment and every 8 weeks for the duration of the study. Ophthalmologic evaluations will be performed at baseline and at 24-week intervals, as well as whenever symptoms indicate a need for a diagnostic evaluation for CMV retinitis. CD4/CD8 counts will be monitored and plasma and polymorphonuclear blood leukocytes will be stored for quantitative HIV RNA and CMV DNA studies at baseline, 16-week intervals, and whenever CMV end- organ disease is diagnosed. Evaluations for non-ocular disease will be performed when clinically indicated and according to predetermined guidelines. Co-enrollment will be permitted in other ACTG studies. This study aims to analyze in detail the relationships between HIV load, CMV load, and CMV end-organ disease in patients with AIDS who are at risk for developing this complication. In addition, the study will describe the natural history of CMV infection in patients receiving a variety of antiretroviral therapies (including HAART), or no anti-HIV therapy at all.